Beijing is a government city, so lots of national and provincial officials floating around, their car of choice seems to be a black Audi, but they seem to be branching out into BMWs, Mercedes, and even land rovers. You can tell who they are by how many traffic rules they ignore, but the police typically don't bother enforcing anything on anyone unless they are in special campaign mode.

Shanghai, Shenzhen, Guangzhou are better. Heck, even Kunming and hangzhou are better than Beijing, given there aren't so many officials in these cities.